Fuel storage tanks of the foregoing type are typically filled from a tank truck by means of a hose that is coupled with an inlet pipe or fitting on the tank. Fuel from the truck is typically pumped into the tank at relatively substantial pressures. Although the pumps are typically operable to shift into a by-pass mode when the pump senses by back-pressure that the tank is full, it is often desirable to stop the fill cycle before the pump goes into by-pass. For example, in some instances the fuel may start spilling out a vent on the tank if the operator waits for the pump to stop the flow. At the same time, however, it is desirable to fill the tank as full as possible, for a number of reasons.
Various types of overfill preventing valves are known in the art. However, not all are readily installable through narrow fittings or inlet pipes on pre-existing tanks. Moreover, not all are simple, effective and reliable.